Objects appear lit even if there is no light source
In your shaders, you shouldn't plug a texture directly into the "Material" output. 

If you don't want your shader to emit light, but only to diffuse external light based on its color, then add a Diffuse shader.



PS: you can tell that a shader is probably wrong when there is a line between two differently-colored sockets. In your case, yellow ("color info") sockets were connected to green ("shader info") sockets.